Protease-containing liquid aqueous detergents are well-known, especially in the context of laundry washing. A commonly encountered problem in such protease-containing liquid aqueous detergents is the degradation phenomenon by the proteolytic enzyme of second enzymes in the composition, such as lipase, amylase and cellulase, or on the protease itself.
As a result, the stability of the second enzyme or the protease itself in the detergent composition is affected and the detergent composition consequently performs less well.
In response to this problem, it has been proposed to use various protease inhibitors or stabilizers. For instance, U.S. Pat. No. 4,566,985 proposes to use benzamidine hydrochloride, EP 376 705 proposes to use lower aliphatic alcohols or carboxylic acids, EP 381 262 proposes to use a mixture of a polyol and a boron compound, and co-pending application EP 91870072.5 proposes to use aromatic borate esters.
It is thus an object of the present invention to provide other reversible protease inhibitors which are effective and suitable for use in an aqueous liquid detergent composition.
In response to this object, the present invention proposes to use peptide aldehydes as reversible protease inhibitors in aqueous liquid detergent compositions.
A particular advantage of the present invention is that peptide aldehydes need only to be used at very low levels in the liquid detergent compositions herein. Thus several parts of materials are made available for other ingredients. This is particularly critical in the formulation of concentrated liquid detergent compositions which are encompassed by the present invention.
Because the peptide aldehydes according to the present invention are so efficient in inhibiting proteases, another advantage of the present invention is that even enzymes which are highly sensitive to proteolytic degradation can now be incorporated in liquid detergent compositions comprising a protease.
The use of peptide derivatives for the inhibition of proteins appears to have been disclosed so far only in therapeutic applications. For instance, EP 293 881 discloses the use of peptide boronic acids as inhibitors of trypsin-like serine proteases. EP 185 390 and U.S. Pat. No. 4,399,065 disclose the use of certain peptide aldehydes derivatives for the inhibition of blood coagulation. J 90029670 discloses the use of optically active alpha amino aldehydes for the inhibition of enzymes in general. See also "Inhibition of Thrombin and Trypsin by Tripeptide Aldehydes", Int. J. Peptide Protein Res., Vol 12 (1978), pp. 217-221; Gaal, Bacsy & Rappay, and "Tripeptide Aldehyde Protease Inhibitors May Depress in Vitro Prolactin and Growth Hormone Release" Endocrinology, Vol. 116. No. 4 (1985), pp. 1426-1432; Rappay, Makara, Bajusz & Nagy. Certain peptide aldehydes have also been disclosed in EP-A-473 502 for inhibiting protease-mediated skin irritation.